The present embodiments relate to a procedure for producing radioactive isotopes for positron emission tomography.
Positron emission tomography (PET) is a nuclear medicine procedure in which the distribution of a radioactively marked substance is displayed. Generally, a PET procedure uses isotopes generated with cyclotrons. For isotope generation, various nuclear reactions are used. The most important reaction is the production of 18F by way of the reaction 18O(p,n)18F.
As a result of the (p,n) reactions, neutron flows of up to 1011 neutrons per second are generated. These neutron flows necessitate considerable expense because of radiation protection needed. In conventional cyclotrons, for example, even behind the radiation protection arrangement, dosage rates of over 100 μSv/h are often reached.
Unless a major expenditure of time is tolerable, the cyclotron is generally set up for one projectile, for example, one type of particle to be accelerated, because of the adaptation made between the high frequency and the given fixed geometry. A cyclotron is generally used to generate PET isotopes. The typical weight of a cyclotron is over 50 t and has a surface area of 6 m2. Cyclotrons are difficult to install because of the size and weight requirements, and the structural requirements of the cyclotron are demanding. To make the cyclotron subsequently accessible to maintenance work and repairs, a total room size of at least 50 m2 for the cyclotron is necessary.
Installing a cyclotron in hospitals and examination equipment is very complicated and expensive, and an area-covering installation of cyclotrons is hardly feasible. Nuclear medicine clinics are generally supplied, for example, externally via distribution centers, with radiopharmaceuticals and biomarkers that are needed for positron emission tomography (PET).
In such external distribution centers, radiopharmaceuticals and biomarkers are as a rule produced in the morning and then sent to the hospitals. Delivery from the external distribution centers takes a certain amount of time. Accordingly, only radiopharmaceuticals or biomarkers with long-lived isotopes are sold. One suitable long-lived isotrope is, for example, the 18F-doped radiopharmaceuticals. The 18F-doped radiopharmaceuticals, whose half-life, which is 110 minutes, is comparatively long. The distribution of 11C- and 13N-doped radiopharmaceuticals via distribution centers is not done, because of the short half-lives of 20 and 10 minutes, respectively. However, 11C radiopharmaceuticals are required for producing specific radiopharmaceuticals and biomarkers that are needed for molecular imaging. Other problems arise from the sale of 18F-doped glucose (known as FDG, for 18F-fluorodeoxyglucose). The distribution of 18F-doped glucose is limited to established radiopharmaceuticals and/or biomarkers that have been clinically evaluated. The distribution is limited because of existing regulations. However, established radiopharmaceuticals and/or biomarkers may not detect early signs of tumors.
Specific examinations in nuclear medicine are subject to narrow limits. Early and specific detection of tumors may be possible with radioactive isotopes. Therefore, it is presently desired that the production of the radioactive isotopes is more flexible and less expense.